Is there an easy way to make a tree in Blender?
Make a Tree with the "Sapling" Addon

If you want to make a tree in Blender, you can use the built-in addon named "Sapling".

To enable it:  


Info header -> File -> User Preferences  

  
Then: 


In the search box, type Sapling
Check the checkbox at the right hand side of the addon
If you want to always have Sapling in your Add menu, then click on the Save User Settings button at the bottom of the screen:   


 
To add a tree to your scene:
SHIFTA -> Curve -> Add Tree  

  
Adjust all the settings:  

 

Since quite a lot of the settings are not labeled in any obvious way, I recommend studying
tutorials on Sapling.

NOTE: You MUST set all the settings the way you want them to be before you do ANYTHING else, otherwise they cannot be changed and the tree will stay that way (i.e. it's parameters are not changeable after it is first created.)

Sapling is very versatile and can create many, many types of trees and bushes. Here are some samples: